unset() is a function for variable management. It will make a variable undefined. Or we can say that unset() is used to null out the value of a given variable. OR Unset() is used to destroy a variable in PHP. In can be used to remove a single variable, multiple variables, or an element from an array.
unlink() is a function for file system handling, unlink() is used to delete files. Suppose you have uploaded a file and wants to delete this file through the coding then unlink() function is used to delete the file.